Monoclonal antibodies have been available for over 25 years and have revolutionalized biomedical research, especially in the areas of disease diagnosis and the treatment of infection and diseases.
The conventional method for the production of monoclonal antibodies involves hybridomas (Köhler & Milstein, Nature 256:495-7, 1975). In this method, splenic or lymphocyte cells from a mammal which has been injected with antigen are fused with a tumor cell line, thus producing hybrid cells. These hybrid cells, or “hybridomas”, are both immortal and capable of producing the genetically coded antibody of a B cell. To select a hybridoma producing a single antibody, the hybridomas made by cell fusion are segregated by selection, dilution, and regrowth until a single genetically pure antibody-expressing cell line is selected. Because hybridomas produce homogeneous antibodies against a desired antigen, they are called “monoclonal” antibodies. Hybridoma technology has primarily been focused on the fusion of murine cells, however human-human hybridomas, human-murine hybridomas, rabbit-rabbit hybridomas and other xenogenic hybrid combinations have been made as well.
Monoclonal antibodies produced by hybridomas, while clearly preferable to polyclonal antibodies because of their specificity and affinity, suffer from certain disadvantages (see Winter & Milstein, 1991 Nature 349:293-9, 1991; Babcook et al., Proc Natl Acad Sci 93:7843-8, 1996). One major disadvantage is that cell fusion is very inefficient, and, as such, the production of a hybridoma for a particular monoclonal antibody that is encoded by only a few antibody producing cells of a host mammal is often not possible.
Polyethylene glycol (PEG) was discovered as an effective “fusogen” for hybridoma production in 1975 (Pontecorvo, Somatic Cell Genet. 1:397-400, 1975) and was rapidly adopted by the scientific community as the fusogen of choice. Current methods of cell fusion have not significantly changed in the last 15 years and most, if not all, routine methods use polyethylene glycol as a fusogen (see Harlow et al, Antibodies: A Laboratory Manual, First Edition 1988 Cold Spring Harbor, N.Y.). However, even with the use of polyethylene glycol, hybridoma production is extremely inefficient, and in many cases only a few hundred hybridomas can be produced from a whole animal spleen. As such, the spleens of several animals are often used in order to produce a single monoclonal antibody of interest.
Accordingly, there is a great need for improved methods for cell fusion, particularly for monoclonal antibody production. The present invention addresses this, and other, needs.